Energy scavenger eats leftover wireless signals

Nikola Tesla high-fives from the grave

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No, it’s not another cute-but-useless contactless charger: a group of researchers led by Manos Tentzeris at Georgia Tech are working on antennae that could scavenge stray wireless signals to power small sensors or microprocessors.

If you’re close enough to a large radio transmitter, harvesting stray energy is pretty straightforward: an old-fashioned long fluorescent tube will at least glow if it’s close enough to a high-power radio transmitter (or, as demonstrated in an art installation, near power transmission lines).

Harvesting “random” signals from the air is more difficult. The ambient signals that surround us all, causing cancer (or not), headaches (or not), or irrational panic (too often) among anyone who notices the transmitter, is of much lower power, and isn’t concentrated around a single frequency.

To turn those stray signals into electricity – in small quantities, so don’t expect a “free” laptop charger anytime soon – the Georgia Tech researchers designed an ultra-wideband antenna that can pick up signals from 100 MHz to around 15 GHz.

The Georgia Tech research has another cool angle to it: the antennas were printed onto flexible material using a modified inkjet that uses refills containing silver and other nanoparticles in an emulsion. By printing onto polymer instead of paper, the group hopes to create antennae operating at up to 60 GHz.

In experiments so far, the antennas have been able to harvest “hundreds of microwatts” from TV bands, successfully powering a temperature sensor using power scavenged from a transmitter a kilometer distant.